"I know the fight inside me is a starter," Roark said. "I can go multiple innings and I build off each inning. It's a big mental part, and I think I've learned a lot, and there's always so much to learn. But I feel like I've proven myself to people, but I've still gotta prove myself even more."

Even though he had a 2.85 ERA in 31 starts in 2014, Roark was the odd man out of the Nationals' rotation last season after the team signed Max Scherzer.

Roark accepted his role in the bullpen last season without complaining. However, he admits now that relieving did not really suit him. He started trying to throw the ball harder and past opposing batters, and his location suffered. He appeared in 40 games and made 12 starts, but his ERA ballooned to 4.38.

"It was just, I think, a big learning experience," Roark said. "A mental [thing], which is always a good thing to have. You always can be mentally sharper, because this game can wear on you, and you want to be as mentally sharp as possible. It helps you build up, I guess, your tolerance for some things that you might not like and you have to deal with regardless."

Roark met with new Nationals manager Dusty Baker to express his desire to begin this season as a starter. Baker said he could not blame Roark, especially after seeing the numbers he put up in 2014. Roark looked sharp Wednesday in the Nationals' Grapefruit League opener. He tossed two scoreless innings, yielding a walk and a hit while striking out three.

At the start of the spring it would appear he has claim to one of the spots in the Nationals' rotation, but after his outing Roark said he would welcome competition.

That will mostly likely come from veteran right-hander Bronson Arroyo. Baker said earlier this week that Arroyo, 39, looked like he still had something left in the tank. Arroyo is competing to take a spot in the rotation from either Roark or Joe Ross, who allowed two runs, both unearned, in two innings during his spring debut Wednesday.

"What I can do is give you an opportunity, that's what I tell them all," Baker said. "I can give you an opportunity, and then it's up to you to put the pressure on us through performance for us to make a decision."